Ventura County Water Supplies Are Safe

CFROG once again incorrectly claims there is evidence of groundwater contamination from oil and gas wells in the Oxnard oil field.

On February 25, 2019, the California State Water Resources Control Board held a stakeholder meeting to present ongoing results of its Regional Groundwater Monitoring Program in the Oxnard coastal plain. The Regional Monitoring Program is conducted in partnership with the U.S. Geological Survey to meet requirements of CA Senate Bill 4 related to oil and gas production.

The presentation on the Regional Monitoring Program in the Oxnard coastal plain was made by Celia Rosecrans of the U.S. Geological Survey.

Here’s what the USGS Regional Monitoring Program study concluded:

  • No mixing of oil field water with overlying groundwater.
  • In three of the 14 wells tested, naturally occurring microbial methane and thermogenic methane associated with oil deposits were detected.
  • Thermogenic gases may result from gas movement along preferential pathways such as wells or from natural migration up through the formation.
  • In the Pleasant Valley area, east of the Oxnard oil field, deep formation brine signatures were detected in 2017 similar to historical data; these detections are a result of groundwater overdevelopment rather than oilfield activities.
  • Results in the Pleasant Valley area are consistent with findings in previous studies that show that detections of these brine-related constituents are related to groundwater supply wells being placed close to naturally occurring hydrocarbon-bearing formations and are not due to oil and gas production activities.
  • Other factors that may affect groundwater quality surrounding the Oxnard
    oil field include managed aquifer recharge to the north, seawater intrusion
    from the southwest, agricultural return flow, and upward movement of
    deep formation brines in response to groundwater development.


“The results of our sampling found we had no evidence or no detections of petroleum hydrocarbons, inorganic constituents, or isotopes that indicate that we had oil field water mixing with the groundwater overlying the oil field.”
-Celia Z. Rosecrans, USGS Geologist



Source: Rosecrans, Celia Z., Landon, Matthew K., and McMahon, Peter B., 2019, Groundwater quality results from the Regional Monitoring Program study of the Oxnard Oil Field, presented at California State Water Resources Control Board Stakeholder Meeting, February 25, 2019, Sacramento, California.

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